Agreement between carotid and LVOT non-invasive cardiac output measurements in ED septic shock patients: a prospective observational study

Sepsis significantly impacts the circulatory system and is associated with high mortality rates, particularly in patients with septic shock who require urgent treatment. Non-invasive cardiac output monitoring is a critical bedside tool for assessing fluid responsiveness. This study aimed to evaluate the agreement between cardiac output measurements obtained from the carotid artery and the left ventricular outflow tract (LVOT) in patients with septic shock in the emergency department (ED). A prospective observational study was conducted on adult patients diagnosed with septic shock and admitted to the ED between October 2023 and October 2024. Cardiac output was calculated using the standard formula (CO = VTI × cross-sectional area × heart rate) for both LVOT and carotid measurements. Agreement between LVOT-derived and carotid-derived cardiac output was assessed using Lin's concordance correlation coefficient, intraclass correlation coefficient, Bland-Altman analysis, and percentage error. Forty patients with septic shock were included in the study. The mean carotid blood flow was 0.855 L/min, while the mean cardiac output measured by LVOT echocardiography was 5.329 L/min. Cardiac output measurements derived from carotid artery VTI and LVOT VTI showed a moderate agreement, as demonstrated by Lin's Concordance Correlation Coefficient of 0.527 (p < 0.001) and an Intraclass Correlation Coefficient (absolute agreement) of 0.695 (p < 0.001). Bland-Altman analysis revealed a bias of - 0.47 (95% CI: -2.11 to 1.17), with a concordance interval ranging from - 10.51 (95% CI: -13.35 to - 7.67) to 9.58 (95% CI: 6.74 to 12.42). Non-invasive cardiac output measurements from the carotid artery exhibited only moderate agreement with those derived from the LVOT, accompanied by wide limits of agreement. This indicates that the two methods should not be utilized interchangeably for clinical decision-making in individual patients. Carotid artery measurements should not be regarded as a direct replacement for LVOT examinations.